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Functional Materials for the Applications of Advanced Gas Sensors

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A special issue of Sensors (ISSN 1424-8220). This special issue belongs to the section "Chemical Sensors".

Deadline for manuscript submissions: closed (28 February 2019) | Viewed by 65678

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Prof. Dr. Youichi Shimizu

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Department of Applied Chemistry, Kyushu Institute of Technology, 1-1 Sensui-cho Tobata, Kitakyushu 804-8550, Japan
Interests: synthesizing and characterizing high functional inorganic materials for application in chemical sensor devices; batteries; and optical-devices based on ceramic materials such as solid electrolyte; oxide thin- & thick- films
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Prof. Dr. Tetsuya Kida

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Department of Applied Chemistry and Biochemistry, Graduate School of Science and Technology, Kumamoto University, Kumamoto 860-8555, Japan
Interests: gas sensors; nanocrystals; electrochemical devices; inorganic-organic hybrids; 2-D materials
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Prof. Dr. Geyu Lu

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College of Electronic Science and Engineering, Jilin University, Changchun, China
Interests: gas sensors; semiconductor oxides; solid electrolytes; nanomaterials; sensing electrodes

Special Issue Information

Dear Colleagues,

High-performance gas sensors are becoming very important in the fields of reactor control, environmental monitoring, and health care technology with gas monitoring, and as an interface for IoT. The use of functional materials, such as nano-powders and nano-films, are one of the new key points for developing high-performance gas sensors. This Special Issue is focused on “Functional Materials for the Applications of Advanced Gas Sensors”. It includes gas sensors based on new or functionally-developed materials, uniquely-designed materials, and so on. The topics include sensors using nanomaterials, nanoparticles, structure-controlled materials, sensor devices based on micro semiconductor, newly designed solid-electrolyte, new sensing methods with electrochemical detection, sensing system, smart system, and gas sensing for health, safety and security care. The MDPI journal, Sensors, is soliciting high-quality papers that document original and significant research works in “Sensors for Advanced Gas Sensors”. We welcome your participation and look forward to your contribution to this Special Issue.

Prof. Dr. Youichi Shimizu
Prof. Dr. Tetsuya Kida
Prof. Dr. Geyu Lu
Guest Editors

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Keywords

Semiconductor, Solid electrolyte, FET- based gas sensors
New transducers based on QCM, SAW, etc.
1D- 2D- 3D- structured nano-materials Nanoparticles
Ceramics, Carbon-related materials
Other new sensing materials for health, safety and security care, and IoT

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Published Papers (10 papers)

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Research

14 pages, 4886 KiB

Open AccessEditor’s ChoiceArticle

Waste Coffee Ground Biochar: A Material for Humidity Sensors

by Pravin Jagdale, Daniele Ziegler, Massimo Rovere, Jean Marc Tulliani and Alberto Tagliaferro

Sensors 2019, 19(4), 801; https://doi.org/10.3390/s19040801 - 15 Feb 2019

Cited by 53 | Viewed by 10583

Abstract

Worldwide consumption of coffee exceeds 11 billion tons/year. Used coffee grounds end up as landfill. However, the unique structural properties of its porous surface make coffee grounds popular for the adsorption of gaseous molecules. In the present work, we demonstrate the use of coffee grounds as a potential and cheap source for biochar carbon. The produced coffee ground biochar (CGB) was investigated as a sensing material for developing humidity sensors. CGB was fully characterized by using laser granulometry, X-ray diffraction (XRD), Raman spectroscopy, field emission-scanning electron microscopy (FESEM), X-ray photoelectron spectroscopy (XPS), thermogravimetric analysis (TGA) and the Brunnauer Emmett Teller (BET) technique in order to acquire a complete understanding of its structural and surface properties and composition. Subsequently humidity sensors were screen printed using an ink-containing CGB with polyvinyl butyral (PVB) acting as a temporary binder and ethylene glycol monobutyral ether, Emflow, as an organic vehicle so that the proper rheological characteristics were achieved. Screen-printed films were the heated at 300 °C in air. Humidity tests were performed under a flow of 1.7 L/min in the relative humidity range 0–100% at room temperature. The initial impedance of the film was 25.2 ± 0.15 MΩ which changes to 12.3 MΩ under 98% humidity exposure. A sensor response was observed above 20% relative humidity (RH). Both the response and recovery times were reasonably fast (less than 2 min). Full article

(This article belongs to the Special Issue Functional Materials for the Applications of Advanced Gas Sensors)

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11 pages, 3543 KiB

Open AccessArticle

Improvement of Sensing Performance of Impedancemetric C₂H₂ Sensor Using SmFeO₃ Thin-Films Prepared by a Polymer Precursor Method

by Tomohisa Tasaki, Satoko Takase and Youichi Shimizu

Sensors 2019, 19(4), 773; https://doi.org/10.3390/s19040773 - 13 Feb 2019

Cited by 8 | Viewed by 3469

Abstract

A sensitive an impedancemetric acetylene (C₂H₂) gas sensor device could be fabricated by using perovskite-type SmFeO₃ thin-film as a sensor material. The uniform SmFeO₃ thin-films were prepared by spin-coating and focusing on the effects of polymer precursor solutions. The prepared precursors and thin-films were characterized by means of thermal analysis, Fourier-transform infrared spectroscopy, ultraviolet–visible spectroscopy, X-ray diffraction analysis, scanning electron microscopy and X-ray photoelectron spectroscopy. It was found that particle growth and increase in homogeneity of the prepared thin-film could be accelerated by the addition of acetyl acetone (AcAc) as a coordination agent in the polymer precursor solution. Moreover, the highly crystallized thin-film-based sensor showed good response properties and stabilities to a low C₂H₂ concentration between 0.5 and 2.0 ppm. Full article

(This article belongs to the Special Issue Functional Materials for the Applications of Advanced Gas Sensors)

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19 pages, 4175 KiB

Open AccessArticle

Co₃O₄/Al-ZnO Nano-composites: Gas Sensing Properties

by Ada Fort, Enza Panzardi, Valerio Vignoli, Mokhtar Hjiri, Mohamed Salah Aida, Marco Mugnaini and Tommaso Addabbo

Sensors 2019, 19(4), 760; https://doi.org/10.3390/s19040760 - 13 Feb 2019

Cited by 22 | Viewed by 4258

Abstract

In this paper, the gas sensing properties of metal oxide nano-powder composites are studied and modeled. The gas sensing properties of mixtures of two different metal oxide nanoparticles, prepared via low-cost routes, are investigated. The responses to both an oxidizing (NO₂) and a reducing gas (CO) are analyzed. The tested composites are obtained by mixing a different percentage of a p-type metal oxide, Co₃O₄, with moderate responses to NO₂ at about 200 °C and to CO at high temperature (above 260 °C), with n-type Al-doped ZnO, which is characterized by a large but unstable response towards NO₂ around 160 °C and a moderate response towards CO around 200 °C. In the oxides mixtures, p-n heterojunctions are formed by the juxtaposition of an n-type and a p-type grain in contact. Consequently, the electronic conductivity is modified and the obtained composite materials show novel characteristics with respect to the base materials. This indicates that predicting the behavior of the composites from those of their components is not possible and it suggests that the hetero-junction behavior has to be studied to understand the sensing properties of the composite materials. The obtained results indicate that the composites containing a significant amount of hetero-junctions exhibit a stable response to NO₂ at room temperature and significant responses towards CO at 160 °C. Full article

(This article belongs to the Special Issue Functional Materials for the Applications of Advanced Gas Sensors)

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14 pages, 4648 KiB

Open AccessEditor’s ChoiceArticle

Synthesis of Cu₂O/CuO Nanocrystals and Their Application to H₂S Sensing

by Kazuki Mikami, Yuta Kido, Yuji Akaishi, Armando Quitain and Tetsuya Kida

Sensors 2019, 19(1), 211; https://doi.org/10.3390/s19010211 - 8 Jan 2019

Cited by 66 | Viewed by 10054

Abstract

Semiconducting metal oxide nanocrystals are an important class of materials that have versatile applications because of their useful properties and high stability. Here, we developed a simple route to synthesize nanocrystals (NCs) of copper oxides such as Cu₂O and CuO using a hot-soap method, and applied them to H₂S sensing. Cu₂O NCs were synthesized by simply heating a copper precursor in oleylamine in the presence of diol at 160 °C under an Ar flow. X-ray diffractometry (XRD), dynamic light scattering (DLS), and transmission electron microscopy (TEM) results indicated the formation of monodispersed Cu₂O NCs having approximately 5 nm in crystallite size and 12 nm in colloidal size. The conversion of the Cu₂O NCs to CuO NCs was undertaken by straightforward air oxidation at room temperature, as confirmed by XRD and UV-vis analyses. A thin film Cu₂O NC sensor fabricated by spin coating showed responses to H₂S in dilute concentrations (1–8 ppm) at 50–150 °C, but the stability was poor because of the formation of metallic Cu₂S in a H₂S atmosphere. We found that Pd loading improved the stability of the sensor response. The Pd-loaded Cu₂O NC sensor exhibited reproducible responses to H₂S at 200 °C. Based on the gas sensing mechanism, it is suggested that Pd loading facilitates the reaction of adsorbed oxygen with H₂S and suppresses the irreversible formation of Cu₂S. Full article

(This article belongs to the Special Issue Functional Materials for the Applications of Advanced Gas Sensors)

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11 pages, 1901 KiB

Open AccessFeature PaperArticle

Selective Functionalization of High-Resolution Cu₂O Nanopatterns via Galvanic Replacement for Highly Enhanced Gas Sensing Performance

by Ju Ye Kim, Soo-Yeon Cho and Hee-Tae Jung

Sensors 2018, 18(12), 4438; https://doi.org/10.3390/s18124438 - 15 Dec 2018

Cited by 8 | Viewed by 4306

Abstract

Recently, high-resolution patterned metal oxide semiconductors (MOS) have gained considerable attention for enhanced gas sensing performance due to their polycrystalline nature, ultrasmall grain size (~5 nm), patternable properties, and high surface-to-volume ratio. Herein, we significantly enhanced the sensing performance of that patterned MOS by galvanic replacement, which allows for selective functionalization on ultrathin Cu₂O nanopatterns. Based on the reduction potential energy difference between the base channel material (Cu₂O) and the decorated metal ion (Pt²⁺), Pt could be selectively and precisely decorated onto the desired area of the Cu₂O nanochannel array. Overall, the Pt-decorated Cu₂O exhibited 11-fold higher NO₂ (100 ppm) sensing sensitivity as compared to the non-decorated sensing channel, the while the channel device with excessive Pt doping showed complete loss of sensing properties. Full article

(This article belongs to the Special Issue Functional Materials for the Applications of Advanced Gas Sensors)

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12 pages, 1659 KiB

Open AccessArticle

Guiding Ketogenic Diet with Breath Acetone Sensors

by Andreas T. Güntner, Julia F. Kompalla, Henning Landis, S. Jonathan Theodore, Bettina Geidl, Noriane A. Sievi, Malcolm Kohler, Sotiris E. Pratsinis and Philipp A. Gerber

Sensors 2018, 18(11), 3655; https://doi.org/10.3390/s18113655 - 28 Oct 2018

Cited by 67 | Viewed by 12437

Abstract

Ketogenic diet (KD; high fat, low carb) is a standard treatment for obesity, neurological diseases (e.g., refractory epilepsy) and a promising method for athletes to improve their endurance performance. Therein, the level of ketosis must be regulated tightly to ensure an effective therapy. Here, we introduce a compact and inexpensive breath sensor to monitor ketosis online and non-invasively. The sensor consists of Si-doped WO₃ nanoparticles that detect breath acetone selectively with non-linear response characteristics in the relevant range of 1 to 66 ppm, as identified by mass spectrometry. When tested on eleven subjects (five women and six men) undergoing a 36-h KD based on the Johns Hopkins protocol, this sensor clearly recognizes the onset and progression of ketosis. This is in good agreement to capillary blood β-hydroxybutyrate (BOHB) measurements. Despite similar dieting conditions, strong inter-subject differences in ketosis dynamics were observed and correctly identified by the sensor. These even included breath acetone patterns that could be linked to low tolerance to that diet. As a result, this portable breath sensor represents an easily applicable and reliable technology to monitor KD, possibly during medical treatment of epilepsy and weight loss. Full article

(This article belongs to the Special Issue Functional Materials for the Applications of Advanced Gas Sensors)

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15 pages, 4802 KiB

Open AccessArticle

Characteristics and Temperature Compensation of Non-Dispersive Infrared (NDIR) Alcohol Gas Sensors According to Incident Light Intensity

by Humaira Hussain, JinHo Kim and SeungHwan Yi

Sensors 2018, 18(9), 2911; https://doi.org/10.3390/s18092911 - 1 Sep 2018

Cited by 10 | Viewed by 5652

Abstract

This paper discusses the output characteristics of the sensor response of infrared ethanol gas detectors based on incident radiation intensity. Sensors placed at each focal point of two elliptical waveguides were fabricated to yield two module combinations and to verify the output characteristics. A thin Parylene-C film was deposited onto the reflector surfaces of one module. The thermal properties were compared between the sensor (2.0 Ø) and sensor with a hollow disk (1.6 Ø), the disk being mounted at the end of one detector. The fabricated sensor modules were placed inside a gas chamber. The temperature was increased from 253 K to 333 K, over the concentration range from 0 to 500 ppm. As the temperature increases by 10 K, the output of sensor (2.0 Ø) without and with Parylene-C coating typically increased by 70 mV and 52 mV, respectively. However, the sensor output with the hollow disk showed an average decrement of 0.8 mV/50 ppm and 1 mV/50 ppm for module without and with Parylene-C deposition, respectively. For concentrations higher than 50 ppm, the estimation error was around ±5%. Further, the sensitivity to temperature variation and the absorbance of infrared (IR) reflection was found higher for Parylene-C coated module. Full article

(This article belongs to the Special Issue Functional Materials for the Applications of Advanced Gas Sensors)

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10 pages, 4135 KiB

Open AccessArticle

Research on a Fast-Response Thermal Conductivity Sensor Based on Carbon Nanotube Modification

by Hongquan Zhang, Bin Shen, Wenbin Hu and Xinlei Liu

Sensors 2018, 18(7), 2191; https://doi.org/10.3390/s18072191 - 7 Jul 2018

Cited by 12 | Viewed by 4663

Abstract

Aiming at solving the slow-response problem of traditional bead-type thermal conductivity gas sensors, a fast-response thermal conductivity gas sensor can be made by using multiwalled carbon nanotubes (MWNTs), combined with the technology of carrier modification, to modify the performance of the sensor carrier. The carrier material, granular nanoscale γ-Al₂O₃/ZrO₂, was synthesized by chemical precipitation, and its particle size was found to be 50–70 nm through SEM. After the carrier material was wet-incorporated into carbon nanotubes, the composite carrier γ-Al₂O₃/ZrO₂/MWNTs was obtained. The results show that the designed thermal conductivity sensor has a fast response to methane gas, with a 90% response time of 7 s and a recovery time of 16 s. There is a good linear relationship between the sensor output and CH₄ gas concentration, with an average sensitivity of 1.15 mV/1% CH₄. Thus, the response speed of a thermal conductivity sensor can be enhanced by doping carbon nanotubes into γ-Al₂O₃/ZrO₂. Full article

(This article belongs to the Special Issue Functional Materials for the Applications of Advanced Gas Sensors)

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10 pages, 3829 KiB

Open AccessArticle

High-Performance Limiting Current Oxygen Sensor Comprised of Highly Active La_0.75Sr_0.25Cr_0.5Mn_0.5O₃ Electrode

by Jie Zou, Qian Lin, Chu Cheng, Xin Zhang, Qinghui Jin, Han Jin, Jinxia Wang and Jiawen Jian

Sensors 2018, 18(7), 2155; https://doi.org/10.3390/s18072155 - 4 Jul 2018

Cited by 5 | Viewed by 4329

Abstract

Zirconia-based limiting current oxygen sensor gains considerable attention, due to its high-performance in improving the combustion efficiency of fossil fuels and reducing the emission of exhaust gases. Nevertheless, the Pt electrode is frequently used in the oxygen sensor, therefore, it restrains the broader application due to the high cost. Quite recently, La_0.75Sr_0.25Cr_0.5Mn_0.5O₃ (LSCM) has been reported to be highly active to catalyze oxygen reduction. Herein, with the intention of replacing the frequently used Pt, we studied the practicability of adapting the LSCM to zirconia-based limiting current oxygen sensor. Through comparing the electrocatalytic activity of LSCM and Pt, it is confirmed that LSCM gave analogous oxygen reactivity with that of the Pt. Then, limiting the current oxygen sensors comprised of LSCM or Pt are fabricated and their sensing behavior to oxygen in the range of 2–25% is evaluated. Conclusively, quick response/recovery rate (within 7s), linear relationship, and high selectivity (against 5% CO₂ and H₂O) in sensing oxygen are observed for the sensors, regardless of the sensing materials (LSCM or Pt) that are used in the sensor. Particularly, identical sensing characteristics are observed for the sensors consisting of LSCM or Pt, indicating the practicability of replacing the Pt electrode by adapting the LSCM electrode to future zirconia-based oxygen sensors. Full article

(This article belongs to the Special Issue Functional Materials for the Applications of Advanced Gas Sensors)

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10 pages, 2683 KiB

Open AccessArticle

Enhanced Hydrogen Detection Based on Mg-Doped InN Epilayer

by Shibo Wang, Xinqiang Wang, Zhaoying Chen, Ping Wang, Qi Qi, Xiantong Zheng, Bowen Sheng, Huapeng Liu, Tao Wang, Xin Rong, Mo Li, Jian Zhang, Xuelin Yang, Fujun Xu and Bo Shen

Sensors 2018, 18(7), 2065; https://doi.org/10.3390/s18072065 - 28 Jun 2018

Cited by 1 | Viewed by 4328

Abstract

It is a fact that surface electron accumulation layer with sheet electron density in the magnitude of ~10¹³ cm⁻² on InN, either as-grown or Mg-doped, makes InN an excellent candidate for sensing application. In this paper, the response of hydrogen sensors based on Mg-doped InN films (InN:Mg) grown by molecular beam epitaxy has been investigated. The sensor exhibits a resistance variation ratio of 16.8% with response/recovery times of less than 2 min under exposure to 2000 ppm H₂/air at 125 °C, which is 60% higher in the magnitude of response than the one based on the as-grown InN film. Hall-effect measurement shows that the InN:Mg with suitable Mg doping level exhibits larger sheet resistance, which accords with buried p-type conduction in the InN bulk. This work shows the advantage of InN:Mg and signifies its potential for sensing application. Full article

(This article belongs to the Special Issue Functional Materials for the Applications of Advanced Gas Sensors)

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